Non-aqueous sil ver halide photographic emulsion processing



Oct. 24, 1967 v v. v. JONES I 3,34

NON-AQUEOUS SILVER HALIDE PHOTOGRAPHIC EMULSION PROCESSING Filed July20, 1964 INVENTOR. V/em/ .V flA/[j United States Patent 0 3,348,946 NOBI-AQUEOUS SILVER HALIDE PHOTOGRAPHIC EMULSION PRQCESSING Viron V.Jones, San Dimas, Califi, assignor to Bell & Howell Company, Chicago,Ill., a corporation of Illinois Filed July 20, 1964, Ser. No. 383,580 18Claims. (Cl. 96-29) This invention relates to a non-aqueous system forprocessing low speed silver halide silver photographic materials and inparticular to processes for developing and stabilizing positive andnegative working silver halide materials and for producing stabilizedimages in silver diffusion transfer materials.

In recent years much effort has been devoted to the investigation ofprocessing exposed silver halide emulsions and especially in the area ofhigh speed processing of such emulsions with the object of speeding orif possible eliminating entirely some of the steps in the course ofproducing a permanent dry negative or print. In the course of theseinvestigations considerable attention has been devoted to developingagents, fixing and stabilizing agents and vehicles by which they areintroduced into the processing reaction, the object being thepossibility of uncovering alternatives to classical silver halideprocessing technology and shorter transition times from exposure tofinished product.

As an example, a considerable effort has been devoted to the evolutionof self-contained processing systems, such as systems in which allconstituents of the processing re action are incorporated in theemulsion carrying sheet and/ or a second processing sheet or in whichthe processing apparatus has the capability of producing a developed anddry record. Examples of such systems include the Land diffusion transfersystems and developout systems such as typified by US. Patent 3,130,000.

As one successor to this technique it has subsequently been found that anon-aqueous system using certain organic compounds such as diols has thecapability of supporting a developing reaction. Such a technique isdescribed in a co-pending application of the present assignee, Ser. No.179,198, filed Mar. 12, 1962.

The complete processing of such emulsions however, requirespost-development treatment in order to obtain a permanent record. Theusual processes which follow development are rinsing, fixation,hardening, washing and drying. Of these five, fixation, washing anddrying are normally required in order to produce a permanent drynegative, though an alternative treatment for prints when extremepermanence is not essential is stabilization and drying.

Such a treatment is necessary because a developd silver halide emulsionnormally contains some residual silver halide unaffected by thedeveloper which is held in the emulsion layer. Since this silver halideis still light sensitive, it must be converted either to a water solublecompound and removed by washing (fixation) or to a stable colorlesscompound (stabilization) if the image is to be permanent. The presentinvention is concerned with the latter treatment. This type oftreatment, namely, the conversion of the remaining silver halide intocompounds which can be relatively inert to heat, light and humidity isparticularly applicable to the rapid processing of films and papersusing small processing machines with heated solutions.

The chemistry of silver halide development and stabilization normallyinvolves the use of solvent to perform several functions. First, asolvent is needed for dissolving the needed reagents such as developers,antifoggants, and stabilizers and provides a vehicle for applying sameto the photographic emulsion; second, a solvent provides the mediumthrough which silver ions can move during the development andstabilization reactions. Up to new water has been the only solvent usedin completely carrying out these steps.

In contrast the present invention contemplates a system for processinglow speed silver halide materials and chemical combinations for use insuch processes which do not require water or water-bearing substances tosupply the necessary solvent action. This is due to the discovery thatthe various compounds used in prior art systems are soluble innon-aqueous solvents without significant variations in the quality ofthe end product. Depending upon the concentration of the variouselements of the processing mixtures, the invention contemplates aprocess not only for development and fixing negative and positiveworking silver halide materials but also a system for processingdiffusion transfer materials. As used herein, low speed emulsionscontemplate silver halide mixtures that do not contain silver iodide.

In the case of normal development and stabilization the processcontemplates the steps of exposing a low speed silver halide emulsion inwhich a developing agent has been incorporated to light in order to forma latent image in the emulsion. Thereafter the exposed emulsion isprocessed by treating it with a mixture comprising a polyhydn'c alcohol,and an alkali and stabilizer which are soluble in the polyhydric alcoholto perform the functions of developing and stabilizing the imagerecorded in the emulsion. The treatment can be accomplished in one ofseveral ways as for example by subjecting the exposed emulsion to aprocessing bath, coating it with a film of liquid, or application bymeans of a web saturated with the mixture and brought in contact withthe emulsion. When the mixture is applied in limited quantities as inthe liquid coating or web technique, heat is applied to the emulsion oremulsion-web combination to speed the process.

In the diffusion transfer application the invention again contemplates aprocess of exposing a low speed silver halide emulsion in which adeveloper has been incorporated to record a latent image and thereaftertreating the emulsion as above. In this case the same formulations asabove, i.e., a polyhydric alcohol and an alkali and a silver halidestabilizing agent now function as complexing agents for the diffusiontransfer process. In addition, many of the alkalis above when dissolvedin a polyhydric alcohol also serve as satisfactory complexing agents.Normally this is accomplished by incorporating a non-aqueous processingmixture as disclosed herein into the transfer or image receiving sheetin which the positive image will ultimately be produced. Again heat isapplied at the moment of contact in order to speed the reaction. In apreferred form, the invention contemplates pre-treatment of the imagereceiving layer in order to provide nucleation sites in the imagereceiving layer i.e., sites or nuclei around which the diffused anddeposited silver grains will grow.

Numerous developing agents have been found to yield satisfactory resultsin the systems of this invention. Examples include hydroquinone, amidol,phenidone and chlorohydroquinone. Numerous non-sodium compounds usableas stabilizing agents are sufficiently soluble in nonaqueous solvents.Examples of such compounds are potassium thios'ulfate, benzenethiosulfonate salts, and salts of mercaptoacetic acid. Examples ofalkalis soluble in the solvents used with this system includes manyorganic bases and certain inorganic compounds such as potassiumcarbonate and potassium hydroxide. The solvents in which these compoundsare soluble are non-volatile polyhydric alcohols or polyols such asethylene glycol, glycerine and their higher homologues. It has beenfound that all of the compounds listed above are sufiiciently soluble insuch polyols to support a developing and fixing reaction as well as adiffusion transfer system.

In addition to its essential solvent function the use of "9 9 apolyhydric alcohol has other advantages in that such substances are morereadily confined to a system than water bearing materials, and are lesssusceptible to problems due to varying pressures or humidity. These andother features of the invention will be made more apparent by referenceto:

FIG. 1, a schematic representation of one apparatus adapted to thecarrying out of theprocess of this invention. In that figure acontinuous strip 10 of a silver halide emulsion moves from a supplyroller 14 over the surface of a rotatable heated drum 16 and is taken upby takeup roller 18. The surface of the drum is heated by an internalheating coil (not shown) connected to a suitable source of electricpower (not shown). A continuousstrip of a second sheet 12. from a supplyroller 26 is pressed firmly against the first sheet by an endless belt28 which passes around a portion of the heated drum 16. The sec ondsheet separates from the first sheet after leaving the heated drum andis taken up by takeup roller 30. The endless belt is disposed aroundadrive roller 32 and a pair of idler rollers 33, 34. Optionally theendless belt may also include a heating element to apply heat to thesecond sheet. An image of an object 40 is focused by lens systems 41 onthe silver halide emulsion before the second sheet is brought in contactwith the first sheet.

As the two sheets move around the heated drum the two layers are pressedtogether and are heated. The stabilizing compound, alkali andnon-aqueous solvent migrate from the layer on the second sheet into thesilver halide emulsion. The latent image is made visible by the actionof the developer and is subsequently stabilized and can be inspectedafter it passes through a light tight opening 42 in a box 44 surroundingthe transport systems In a developing and stabilizing process the systemcontemplates a mixture comprising a non-aqueous solvent and an alkaliand a stabilizing agent. To this basic mixture other additivesperforming such functions as preand sorbit-ol, C H (OH) The silverhalide stabilizing agents which are added are agents which have beenfound to have the characteristic of sufficient solubility in any of theabove polyols to accomplish their stabilizing function satisfactorily.These agents include potassium thiosulfate, potassium thiocyanate,benzene thiosulfonate salts, thioglycerol, thiourea and salts ofmercaptoacetic acid. Alkalis soluble in these alcohols include organicbases such as quar-, ternary ammonium hydroxides and amines and inparticular amines such as ethanolamine, diethanolamine, triethanolamine,salts of these ethanolamines and sodium bisulfite and salts of theseethanolamines and acetic acid and inorganic bases such as potassiumcarbonate and potassium hydroxide.

When applied in a conventional bath to a developed silver halideemulsion the result is a fully stabilized negative or in the case ofreversal material, a fully stabilized positive image. In addition toapplication in the conventional manner several other methods are alsopossible such as application by means of a slit applicator or rollercoater.

In a rapid processing system it is contemplated that the mixture will beincorporated in a web such as is used in an apparatus similar to the onedescribed in conjunction with FIG. 1 or by other means in which themixture can be applied in small, controlled amounts. In suchapplications it is contemplated that the developer will be incorporatedin the emulsion prior to exposure and the stabilizing formulationapplied as above. This imposes a requirement that the developing agentused also be soluble in a polyhydric alcohol. Developers which have beenfound to be sufficiently soluble in these alcohols include hydroquinone,methyl hydroquinone, amidol, phenidone, paraphenylene diamine, metol,chlorohydroquinone, pyrogallol and ascorbic acid.

Prior to incorporation in a web for use in a rapid processingapplication a processing mixture would typically be prepared in thefollowing manner: a stabilizing agent such as potassium thiosulfate andan alkali such as potassium carbonate are added to ethylene glycol. Thisis done by adding to approximately 11 parts by weight of ethylene glycolheated to approximately C. one part by weight of potassium thiosulfatewith stirring. After this solution is complete 0.5 part by weight ofpotassium carbonate is dissolved in the solution and the mixture isallowed to cool slightly. A porous paper such as filter paper or thatused for paper chromatography is bathed in the glycol solution andallowed to remain until saturated. When a web treated with this solutionis brought in contact with an exposed low speed silver halide sheet andheld there approximately one minute at a temperature of 60 C., theresult is a negative of satisfactory contrast and good stability. Whensimilarly applied to a positive working emulsion such as KodakAutopositive paper, a stabilized direct positive is the result.

By. the simple expedient of varying the concentration of the potassiumthiosulfate in the processing mixture these same constituents areequally well adaptable to a diffusion transfer system. In this instanceonly 0.02 part by weight of potassium thiosulfate, that is,approximately one-fiftieth of the original concentration, is used intheprocessing mixture. When an image receiving layer saturated with thepreceding solution is applied to a slow speed silver halide paper andprocessed for about a minute at approximately 65 C. a positive image isproduced on the transfer sheet. As the preceding example illustrates,the same constituents used in a developing and stabilizing process areequally well adapted to a diffusion transfer process by adjusting theconcentration of the various components usedjIn this case thestabilizing agent now functions as a mobilizing or silver transferagent.

In addition to the preceding formulations, it has been found that theorganic bases used as alkalis in the development and stabilization ofpositive and negative working materials also are capable of functioningas complexing agents in a diffusion transfer process when combined witha polyhydric alcohol. These organic bases include quartenary ammoniumhydroxides and amines such as ethanola-mine,diethanolamine,triethanolamine, salts of the preceding ethanolamines andsodium bisulfite and salts of the preceding ethanolamines and aceticacid. As illustrated in more detail below, potassium sulfite is also asatisfactory complexing agent.

The diffusion transfer process is enhanced by prior preparation of theimage receiving sheet. Such preparation involves providing nucleationregions in the image receiving layer prior tosaturation with thepolyol-complexing agent mixture of. this invention. Nucleation of thesheet support provides means whereby the precipitation of metallicsilver can be controlled both as to concentration and disposition in thereceiving layer. One example of the way in which the sheet can benucleated is as follows:

The paper is first bathed in a .001 normal silver nitrate solution andis then blotted free of this liquid and bathed in a .001 normal sodiumsulfide solution and is again blotted free of the liquid and. dried.This nucleated sheet is then ready for immersion in the various polyolbaths by which the processing fluid is incorporated in the imagereceiving layer.

Other illustrations of possible processing mixtures follow. A nucleatedpaper prepared according to the preceding technique and bathed in asolution of approximately l1 parts by weight of ethylene glycol and onepart by weight of potassium sulfite provides another image reeeivinglayer for a diffusion transfer system. Contact between this sheet and adeveloper-incorporating low speed silver halide emulsion forapproximately one minute at a temperature of approximately 85 C.produces a positive image in the nucleated sheet. A similarly nucleatedsheet bathed in a solution of approximately 11 parts by weight ofethylene glycol and approximately 5 parts by weight of diethanolamineillustrates still another variation in the application of the inventionto a diffusion transfer system. By maintaining contact between anucleated sheet saturated with this mixture and a developerincorporating silver halide emulsion at approximately 60 C. forapproximately two minutes a positive image is formed in the nucleatedsheet.

As an additional refinement it may be desired to incorporate theprocessing fluid into a web in a viscous form to avoid the handling ofwet materials. The processing liquid can be made viscous by one ofseveral methods well known in current practice in the art such as byadding to the processing solution a gelling agent. When used in thisform, heat is an essential requirement in order to melt the solid geland put the web in condition such that the development and stabilizationor transfer reaction may go forward. The preferred ranges of temperaturefor processing in accordance with this further refinement have beenfound to "be approximately 60 C. to approximately 130 C.

What is contemplated then is a non-aqueous photochemical systemespecially useful in the rapid processing of low speed silver halideemulsions. This utility encompasses the development and stabilization oflow speed silver halide emulsions as well as difiusion transferapplications.

I claim:

1. A non-aqueous process for developing and stabilizing a photographicimage comprising the steps of:

exposing a low speed photosensitive silver halide emulsion disposed on asheet to light for the formation of a latent image,

applying a developing agent to the exposed emulsion to render the latentimage visible and thereafter, processing the emulsion by applying amixture of a polyhydric alcohol and a stabilizing agent selected fromthe group consisting of potassium thiosulfate, potassium thiocyanate,benzene thiosulfonate salts, thioglycerol, thiourea and salts ofmercaptoacetic acid to the developed emulsion to stabilize the imagerecorded therein. 2. A non-aqueous process for developing andstabilizing a photographic image comprising the steps of:

exposing a low speed photosensitive silver halide emulsion disposed on asheet to light for the formation of a latent image, the sheet havingincorporated therein a developing agent and thereafter,

processing the emulsion by applying a mixture of a polyhydric alcohol,an alkali and a stabilizing agent, the alkali being selected from thegroup consisting of amines, quarternary ammonium hydroxides, potassiumcarbonate and potassium hydroxide and the stabilizing agent beingselected from the group consisting of potassium thiosulfate, benzenethiosulfonate salts, potassium thiocyanate, thioglycerol, thiourea andsalts of mercaptoacetic acid to activate the developing agent anddevelop and stabilize the image recorded therein.

3. A non-aqueous process for developing and stabilizing a photographicimage comprising the steps of:

exposing -a low speed photosensitive silver halide emulsion disposed ona sheet to light for the formation of 6 ethanolamines and sodiumbisulfite, and salts of said ethanolamines and acetic acid thestabilizing agent being selected from the group consisting of potassiumthiosulfate, benzene thiosulfonate salts, potassium thiocyanate,thioglycerol, thiourea and salts of mercaptoacetic acid to activate thedeveloping agent and develop and stabilize the image recorded therein.

4. A process according to claim 3 in which heat is applied during theprocessing step to maintain the emulsion and mixture at a temperature inexcess of 60 C.

5. A process according to claim 2 wherein the polyhydric alcohol isselected from the group consisting of ethylene glycol, glycerol,erythritol, arabitol and sorbitol.

6. A non-aqueous silver diffusion transfer process comprising the stepsof:

exposing a low speed photosensitive silver halide emulsion disposed on afirst sheet to light for the formation of a latent image, the firstsheet having incorporated therein a developing agent,

contacting the emulsion side of the first sheet with a second sheet intowhich has been incorporated a polyhydric alcohol and a complexing agentselected from the group consisting of potassium sulfite and the amines,and

applying heat to the contacted sheets whereby the complexing agent istransferred to the first sheet, the developing agent is activated, aportion of the silver halide in the emulsion is dissolved in thecomplexing agent and an image-wise transfer of silver to the secondsheet is completed.

7. A diffusion transfer process according to claim 5 wherein thecomplexing agent is a mixture of an alkali and a silver transfer agent,the alkali being selected from the group consisting of amines,quaternary ammonium hydroxides, potassium carbonate and potassiumhydroxide and the silver transfer agent being selected from the groupconsisting of potassium thiosulfate, benzene thiosulfonate salts,potassium thiocyanate, thioglycerol, thiourea and salts ofmercaptoacetic acid.

8. A non-aqueous silver diffusion transfer process comprising the stepsof:

exposing a low speed photosensitive silver halide emulsion disposed on afirst sheet to light for the formation of a latent image, the firstsheet having incorporated therein a developing agent,

contacting the emulsion side of the first sheet with a second sheet intowhich has been incorporated a polyhydric alcohol and a complexing agentselected from the group consisting of potassium sulfite, ethanolamine,diethanolamine, triethanolamine, salts of said ethanolamines and sodiumbisulfite, and salts of said ethanolamines and acetic acid, and

applying heat to the contacted sheets whereby the complexing agent istransferred to the first sheet, the developing agent is activated, aportion of the silver halide in the emulsion is dissolved in thecomplexing agent and an image-wise transfer of silver to the secondsheet is completed.

9. A process according to claim 6 in which the second sheet has beennucleated prior to exposure by a process comprising the steps of:

bathing the sheet in a dilute silver nitrate solution,

bathing the sheet in a dilute sodium sulfide solution,

and thereafter drying the sheet.

10. A process according to claim 6 in which the heat supplied to thecontacted sheets is suflicient to maintain the temperature of the sheetsin excess of 60 C.

11. A process according to claim 6 in which the polyhydric alcohol isselected from the group consisting of ethylene glycol, glycerol,erythritol, arabitol and sorbitol.

12. A composition of matter for use in stabilizing low speedphotosensitive silver halide emulsions comprising a mixture of apolyhydric alcohol, an alkali and a silver halide stabilizing agent, thealkali being selected from the 7 group consisting of amines, quaternaryammonium hydroxides, potassium carbonate and potassium hydroxide and thestabilizing agent being selected from the group consisting of potassiumthiosulfate, potassium thiocyanate, benzene thiosulfonate salts,thioglycerol, thiourea and salts of mercaptoacetic acid.

13. A composition of matter for use in stabilizing low speedphotosensitive silver halide emulsions comprising a mixture of apolyhydric alcohol, an alkali and a silver halide stabilizing agent, thealkali being selected from the group consisting of potassium carbonate,potassium hy droxide, ethanolamine, diethanolamine, triethanolamine,salts of said ethanolamines and sodium bisulfite, and salts of saidethanolamines and acetic acid and the stabilizing agent being selectedfrom the group consisting of potassium thiosulfate, benzenethiosulfonatesalts, potassium thiocyanate, thioglycerol, thioureaandsalts of mercaptoacetic acid to activate the developing agent anddevelop and stabilize the image recorded therein.

14. A composition of matter according to claim 12 in which thepolyhydric alcohol is selected from the class comprising ethyleneglycol, glycerol, erythritol, arabitol and sorbitol.

15. A composition of matter for use with a low speed silver halideemulsion in a silver diffusion transfer reversal system comprising amixture of a polyhydric alcohol and a complexing agent selected from thegroup consisting of potassium sulfite and the amines.

16. A composition of matter for use with a low speed silver halideemulsion in a silver diffusion transfer reversal system comprising amixture of a polyhydric alcohol, an

alkali and a silver transfer agent, the alkali being selected from thegroup consisting of amines, quaternary ammonium hydroxides, potassiumcarbonate and potassium hydroxide and the silver transfer agent beingselected from the group consisting of potassium th osulfate, benzenethiosulfonate salts, potassium thiocyanate, thioglycerol, thiourea andsalts of mercaptoacetic acid.

17. A composition of matter for use with a low speed silver halideemulsion in a silver diffusion transfer reversal system comprising amixture of a polyhydric alcohol and a complexing agent selected from thegroup consisting of potassium sulfite, ethanolamine, diethanolamine,triethanolamine, salts of said ethanolamines and sodium bisulfite, andsalts of said ethanolamines and acetic acid.

18. A composition of matter according to claim 15 in which thepolyhydric alcohol is selected from the. class comprising ethyleneglycol, glycerol, erythritol, arabitol and sorbitol.

References Cited UNITED STATES PATENTS 6/1965 Hass 96-66

1. A NON-AQUEOUS PROCESS FOR DEVELOPING AND STABILIZING A PHOTOGRAPHICIMAGE COMPRISING THE STEPS OF: EXPOSING A LOW SPEED PHOTOSENSITIVESILVER HALIDE EMULSION DISPOSED ON A SHEET TO LIGHT FOR THE FORMATION OFA LATENT IMAGE, APPLYING A DEVELOPING AGENT TO THE EXPOSED EMULSION TORENDER THE LATENT IMAGE VISIBLE AND THEREAFTER, PROCESSING THE EMULSIONBY APPLYING A MIXTURE OF A POLYHDRIC ALCOHOL AND A STABILIZING AGENTSELECTED FROM THE GROUP CONSISTING OF POTASSIUM THIOSULFATE, POTASSIUMTHIOCYANATE, BENZENE THIOSULFONATE SALTS, THIOGLYCEROL, THIOUREA ANDSALTS OF MERCAPTOACETIC ACID TO THE DEVELOPED EMULSION TO STABILIZE THEIMAGE RECORDED THEREIN.